Time keeping mechanism



April 5, 1932. A. FVPOOLE 3,852,396

TIME KEEPING MECHANISM Original Filed March 25. 1927 3 Sheets-Sheet 1INVENTOR flrZ/aati'loak April. 5, 1932. A, F, OOLE 1,852,896

TIME KEEPING MECHANISM Original Filed March 25. 1927 3 Sheets-Sheet 22192 v Q i lNVNTOR flZ/zarif ooze zfsATTORNEY April 5', 1932, F Lfifiiifi TIME KEEPING MECHANISM Original Filed March 25. 1927 I5Sheeis-Sheet 3 Z'SATTORNEY Patented Apr. 5, 1932 UNITED STATES,

PATENT OFFICE ASSIGNOB TO POOLE MANUFACTURING 60.,

CORPORATION OF NEW YORK TIME KEEPING MECHANISM Application filed March25, 1927, Serial No. 178,382. Renewed March 27, 1930.

This invention relates to electric time keeping devices, and has for itsobject the provision of a simple and accurate mechanism for drivingclockwork, recording apparatus, or

55 other devices in which a uniform rate of motion is desired. In suchdevices, as well as in clockwork, the frictional load on the timekeeping mechanism tends to vary somewhat and accordingly affects theaccuracy of the 1 time keeping.

vention is to provide a driving mechanism whose power will increase ordecrease according to the demands upon it, leaving a substantiallyconstant residuum of drive the pendulum or other time determiningelement, so that a variation in the external load will not react on thetime keeping. Another object of my invention is to provide a vibratorymotor, an electromagnetic means for actuating it, the vibratory motorbeing adapted both ,to deliver power to an external gear train and tomaintain a time keeping element such as a pendulum or balance wheel invibration.- A' furtherobject of my invention is to provide a vibratorymotor and timekeeping element as described above and means forsynchronizing the vibratory motor with the time keeping element. Theseand other objects of my invention will be apparent to those skilled inthe art from the accompanying drawings and specifications.

In the accompanying drawings forming part of this specification andillustrating the principles of the mechanism, Fig. 1 is a side elevationof the mechanism showing the general arrangement ofparts.

Fig. 2 is a rear elevation partly in section taken substantially alongthe line 2-2 of Fig. 1.

Fig. 3 is a detail view illustrating the escapement and contactmechanism.

Fig. 4 is a perspective view of the pallets.

Fig. 5 is a plan view of the mechanism as viewed from above with thependulum omitted. 7

Fig. 6 is a detail view of one form of pallet drive element. a y

The same reference numerals refer to the 50 same parts throughout thevarious views.

One object of the present in-' power to the shaft 5 engages Referringnow to Fig. 1, the load or driven device which it is desired to operateat a regular rate of movement is represented by the clock 1, though itwill be understood that the invention is equally applicable to variousforms of meters, recording instruments, and other devices where anelement must be moved according to time. The time determining element isrepresented by the pendulum 2, though it will be understood that anyequivalent element such as a balance wheel may be employed.

lnmany instances the load of the clock or driven device becomes ratherheavy for the ordinary clock mechanism, due to dust, paper friction, orother causes, and the power applied to the pendulum 2 may become soweakened as to afiect its time keeping qualities. To overcome thisdiiiiculty, I provide a second periodic device to carry the load, thisdevice consisting of a vibratory electro-magnetic motor 3, having anarmature 4: mounted on the shaft 5, which also carries the balance wheel6, and is controlled in its oscillation by the spiral spring 7. Thisbalance wheel is driven thru the attraction of the armature 4; by thepole pieces 8, 8, or the electro-magnet 9, which is periodicallyenergized by the action of an electric contact operated by the pendulum2, as will be described.

The electric current for the electro-magnetic motor 3 may be obtainedfrom any suitable source. For example, in the mechanism illustrated drycells such as the ordinary flashlight battery are contained in the post30 and the current is conducted out thru the clip 31 and wire'32 to theelectro-magnetic motor 3 and thence to the wire 83 toan electric contactdevice which will be described, after which it is grounded back thru theframe to the battery. The source of supply of electricity may vary ofcourse to suit the conditions of various installations.

A tooth or pin 10 mounted on an arm of the teeth of a. fork 11 as theshaft 5 oscillates, the pin 10 generally swinging free of the fork forthe end portions of its swing (see Fig. 2) and picking it up again onthe return. The fork 11 is pivoted at 12 and carries at its other endthe pallets 13 and 13', which are .thus rocked to and fro with adefinite motion regardless of variations in the amplitude of vibrationof the armature 4--due to the fact that the pin 10 is' only in drivingengagement during the middle portion of its swing.

The pallets 13, 13', alternately engage the sides of the teeth of anescapement wheel 14, and the faces of the pallets are properlyinclined-to feed the wheel 14 around one tooth at a time. The wheel 14turns the pinion 15, by which motion is transmitted thru any suitablereduction gearing 16 to the clock 1 or'other apparatus which it isdesired to drive.

The regularity with which this clock or other driven apparatus 1 isoperated depends of course on the rate of vibration of the armature 4 ofthe vibrating motor 3. It is desired to maintain this rate of vibrationconstant, regardless of ordinary variations in the amount of the load 1,which necessitates that the power input to the motor 3 must increase asthe load increases, and vice versa. A vibrating type of motor 3 is usedbecause it has itself a certain natural period of vibration, and becauseit avoids brush friction and other ditficulties of a rotary motor. To

regulate the speed and power output of the' vibratory motor 3 there isprovided a pendulum 2 or other time determining device and a flexible,leaf spring 17.

The spring 17 at one end is anchored to the frame, adjacent but at oneside of the axis of oscillation of the pendulum, so that the free end ofthe spring may flex in the directions of oscillations of the pendulum 2.An impulse element 18 in the nature of a lever is pivoted between itsends by a pivot 19. One end of the element or lever 18 has a nose 20which rides over the teeth of wheel 14, so that as the wheel 14 isrotated step by step, its teeth will rock the lever 18 in one direction,gravity holding the nose 20 against the teeth of the escapement wheel.The other end of the lever 18 extends laterally of its length and intothe flexing path of the free end of the spring 17 so that the lateralarm of leverl8 may engage the free end of the spring 17 and flex it awayfrom the position into which it is urged by its own resiliency. I

The free end of the spring 17 carries a contact button 21 which engageswith a contact screw 22 carried by and insulated from the frame of theclock and extending endwise in a direction to oppose the movementof thebutton 21. The button 21 is urged against the end of the contact screw22, by the resil- '22. The spring 17 is tensloned by. the leftiency ofthe spring 17, .and the screw 22 acts as a limit stop for the spring 17.When the lever 18 is rocked by an operation of the escapement wheel; itslateral arm will engage with the free end of spring 17 and flex it in adirection to carr the button 21 away from the screw 22, as s own in Fig.2.

the .rig t.

The spring 17 extends somewhat beyond the button 21.and into the path oftravel of the head of a screw 23 which is threaded through the pendulum2, intermediate of its ends, and moves with the pendulum duril ig itsoscillations The spring 17 is disconnected from the pendulum except forthe bearing contact of its free end upon the screw 23. 1V hen thelever-18 is rocked positively by the teeth of the escapement wheel, thelat eral arm which engages and flexes the spring 17 will swing upwardlythrough an are which terminates substantially tangent to the spring 17and hence the spring'will hold the lever 18 frictionally in thisposition until the pendulum flexes the spring and releases the lever ina manner to be explained presently.

As the pendulum swings to the right beyond its midposition, as observedin igs. 2 and 3, the head of the screw 23 will travel away from thespring 17 as shown in full lines in Fig. 3. As the pendulum swings inthe reverse direction or toward the left in Figs. 2 and 3, it will-move,unaffected by spring 17 until it closely approaches its midposition ofswing, as shown in Fig. 2, at which time the head of the screw'23engages with the free end of the spring 17 that has been flexed bylever18, whereupon the pendulum carries with it and further flexes the freeend of the spring during the remainder of its swing to the left. Themovement of the spring 17 with the pendulum releases the lever 18, whichis then free to action of gravity and insert its nose 20 between theteeth of the escapement wheel. Since the escapement wheel is beingoperated rotate by the step by step from the vibratory electric motorwhile the ifl'rdulum is oscillating, the escapement wheel will havemoved a half step position ,from that shown in Fig. 2 into the positionshown in- Fig. 3, while the pendulum swings from mid-position to theleft and back again to mid-position, which allows the nose 20 to enterthe space between the escapeas the pendulum moves toward the right, the

button 21 may engage the screw 22 and close the electric circuit.

It will be noted that the button 21 is spaced from the screw 22 when thespring 17 is picked up by the screw 23 of the pendulum during itsleftward swing (F i 2), and the spring ceases its action on t e pendulumduring the swing of the pendulum to the right when the button 21 engagesthe screw ward swin of the pendulum, and exerts a retarding orce thereonwhich is converted into a ropelling force during the swing to Inasmuchas the action of the spring on the pendulum in a proplelling directionis somewhat longer than t -ment wheel teeth, at which time the lateral eretard- 1 I after the contact 21 meets '18 represents sufiicient powering action, the net result is a propelling impulse on the pendulum whichmaintains itin oscillation. The adjustment of the screws 22 and 23provides for a regulation of the amount of the impulse given thependulum.

The spring 17 is mounted in the pendulum 2 under a certain amount ofinitial tension, as determined by the adjustable screw 20: mounted'inthe pendulum rod, so that the fiexure given the spring 17 by the elementto drive the pendulum. Since the throw of the element 18 is fixed, theamount of power transmitted to the pendulum spring 17 and pendulum 2depends principally on the strength and initial tension of the spring17l In operation, the contact 22 as shown in Fig. 3, the screw 2a swingson with the pendulum free of the spring 17, and picks it up again on thereturn strokeas shown in Fig. 2.

The method by which the pendulum 2 regulates the vibratory motor 3-sothat the two stay in synchronism is as follows:

When the pendulum 2 swings to the right, the electric contact 21 carriedon the spring 17 meets the contact screw 22 and closes an electriccircuit thru the magnet 9, which tends to accelerate the armature 4. Thecircuit remains closed until the armature 4:, in passing thru the middleof its swing, actuates the pallets which drive the wheel 14 and thusswings the element 18 against and flexes the spring 17 away from thecontact screw 22 and breaks the circuit.

To start the clock, the pendulum is first started swinging in the as thecontact 21, 22, is closed, the armature 1 which has been held somewhatretracted by hand is released, so as tobreak the contact 21, 22,immediately after it is madeit being necessary to start the armature 4and pendulum 2 initially in substantially the proper phase-ofsynchronism, as the clock will not start by the pendulum alone.

The length of time that the electric power is applied is measured fromthe instant the pendulum action closes the circuit until the instant theaction of the vibratory armature opens it. Therefore, if the period ofthe vibratory armature tends to lag behind, the

- length of time that the electric power is apthe pendulum within aplied will increase. The increased power then tends to accelerate thearmature action; and as the armature action catches up with the periodquicker and the power impulses of the vibratory motor correspondinglydiminishso that the armature keeps in synchronism with fraction of avibration. The power input, with constant potential, is of courseproportional to the length of time that the circuit is closed; thatlength of time is proportional to the'lag of the armature, and that lagis in general proportional usual way, and then. i

of the pendulum, the cut-oil comes to the load; so that the power inputis substantially proportional to the load of the driven apparatuswithinthe limits of synchronism. This permits the desired functioning of thedevice.

- The natural period of the vibrating armature 1, considered as abalance wheel, is so proportioned that it would be slightly slower thansynchronism were it not for the impetus of the magnetic impulses. Themagnetic impulses tend to accelerate the armature and make its periodfaster. The reason for making the natural or unassisted period of thearmature slightly slower than that of the pendulum 2 is that thispermits the armature tohave an increasing lag with the increasing load,this lag being utilized to bring in the compensating increase in powerinput as described.

The vibratory armature t and the pendulum 2 are of course in synchronismso far as vibration per minute are concerned, so that power drawn fromthe armature 4 can drive the pendulum 2the lag referred to being no morethan a fraction of a vibration.

Tn the foregoing l have described one embodiment of my invention forpurposes of. illustration, and it will be understood that it is notlimited to the particular form shown, but is susceptible to variousmodifications and changes oi arrangement, form, and details to adapt itto various installations, as will be apparent to those skilled in theart, without departing from the scope of the invention as specified inthe following claims.

ll claim:

1. In a time keeping apparatus, the combination of a time determiningelement having a periodic motion, a vibratory motor having a naturalperiod somewhat slower than the time determining element, and electricalmeans for increasing the speed of the motor so that it is maintained insynchronism with the time determining element.

p 2. In a time keeping apparatus, the combination of a time determiningelement having a periodic motion,'a vibratory motor of theelectro-magnetic type, means operated by said time determining elementfor energiz-.

ing a periodic motion, a vibratoy motor, means for keeping the timedetermining element and the vibratory motor in -synchronism, includingmeans by which the motor may supply power to drive mining element.-

4. In a time keeping apparatus, the combination ofa time determiningelement have the time detertime keeping apparatus, the com- 1 -binationof a time determining element havportion of the power ing a periodicmotion, a vibratory motor, an external load, means for keeping the timedetermining element'and the vibratory motor in synchronism, includingmeans by which a portion of the power of the motor is diverted to drivethe time determining element, while the balance of the power of themotor is applied to the external load.

5. In a time keeping apparatus, the combination of a time determiningelement having a periodic motion, a vibratory motor, an external load,means for keeping the time determining element and the vibratory motorin synchronism, includ ng means by which a of the motor is diverted todrive the time determining element, while the balance of the power ofthe motor is applied to the external loads, and means for varying thepower of the motor in proportion to the external load.

6. In a time keeping apparatus, the combination of a t me determiningelement having a periodic motion, a vibratory motor, means for drivingthe time determining element by mechanical energy derived from themotor, and means for regulating the motor by electrical energycontrolled in synchronism with the period of the t me determiningelement, whereby the time ment and the vibratory motor may bemaintained' in synchronism.

7. In a time keeping apparatus, the combination of a time determiningelement having a periodic motion, a vibratory motor of theelectro-magnetic type, means for drivin the time determining element bymechanical energy derived from the motor, and means for regulating themotor by electrical energy controlled in synchronism with the period ofthe time determining element, whereby the time determining element andthe vibratory motor may be maintained in synchronlsm.

8. In a time keeping apparatus, the combination of a time determiningelement having aperiodic motion, a vibratory motor of theelectro-magnetic type, means operated by said time determ ning elementfor energizing said motor, means operated by said motor forde-energizing said motor, said de-energizing means being operated in themiddle portion motor so as tobc independent of the amplitude of vibraton,

the amount of power applied to said motor depending on the lag of themotor, whereby the motor and the time determining element are kept insynchronism.

9. In a time keeping apparatus, the combin ation of a vibratory motor,an escapement wheel driven by said motor, a rocker arm driven by saidescapement wheel, a t me determining element having a periodico.scilla-. 'tory motion. a driving spring urging said time determiningelement in one direction, said driving spring being stressed from thedetermining ele-' 1 somewhat in said opposite operation of the rockerarm by saidvibratory motor, and an electric circuit controlling saidmotor and periodically rendered effective by said spring.

10. In a time keeping apparatus, the combination of a vibratory motor ofthe electromagnetic type, -an escapement wheel driven by said motor, arocker arm driven by said escapement wheel, a time determining elementhaving a periodic oscillatory motion, a driving spring urging said timedetermining element in one direction, an" electric circuit periodicallyrendered effective by said spring and controlling said vibratory motor,said rocker arm being arranged to operate in conjunction with saidspring to cut off the flow of power and at the same time to store insaid spring mechanical energy by which the time determining element ismaintained in its periodic oscillation.

11. In a time keeping apparatus, the combination of a vibratory motorhaving a variable amplitude of vibration. oscillatory gearing arrangedto be driven during the middle portion of the vibration, the vibratorymotor swingine' free at the extremities of its vibrat on, palletsperiodically oscillated by said gearing, an escapement wheel driven bysaid pallets, an impulse member driven by said escapement wheel, a timedetermining element having a periodic motion of oscillation. a drivingspring urging said element in one direction and stressed by said elementwhile said element is moving in the opposite direc- 85 tion, energvbeing periodically stored in sa d bv the action of the impulse member,

p g which stresses said spring somewhat in said opposite direction, saidimpulse member being mainta nedin position by friction with the springuntil said spring is stressed by said element. and means controlled bysaid spring for controlling said motor.

12. In a. time keeping apparatus, the comb nation of avibratory motorhaving a variable amplitude of vibration. oscillatorygearing arranged tobe driven during the middle portion of the vibration. the vibratorymotor swinging free at the extremities of its vibration, palletsperiodically oscillated bv said gearing, an escapement wheel driven bysaid pallets, an impulse member driven by said escapement wheel, a timedetermining element having a periodic motion of oscillation, a drivingspring urging said element in one direction and'stressed by said elementwhile said element is moving in the opposite direction, energy beingperiodically stored in pulse member, which stresses said spring pulsemember having an arcuate motion terminating substantially tangent tosaid spring, whereby a definite amount of fiexure is given the drivingspring irrespective of slight direction, said im termining el with eaching a periodic variations in the travel of the impulse mem- 13. In atime keepingppparatus having an electric circuit, the com ination of anescapement wheel having teeth, oscillatory pallets arranged to drive theescapement wheel thru lateral engagement with the teeth, and a rockerarm operated by engagement with the end of the teeth, the axis ofoscillation of the rocker arm being at right angles to the axis ofoscillation of the pallets, and means operated by the rocker arm forbreaking the electric circuit.

14. In a time keeping apparatus having an electric circuit, thecombination of an escapement wheel having teeth, oscillatory palletsarranged to drive the escapement wheel thru engagement with two sides ofthe teeth, a rocker arm'operated by engagement with a third side of thesame teeth, and means operated by the rocker arm for breaking theelectric circuit.

15; In a time keeping apparatus, the combination of a time determiningeiement having a periodic moti'on, a driving spring stressed thereby andurging said element in one direction, a vibratory motor arranged todeliver energy to said driving spring with each vibration of the timedetermining element, and means for regulating the ampli tude of thevibratory motor, whereby it may be maintained in synchronism with thetime determining element.

16. In a time keeping apparatus, the combination of a time determiningelement havmotion, a driving spring stressed thereby and urging saidelements in one direction, a vibratory motor arranged to deliver energyto said driving spring with each vibration of the time determiningelement, and means for regulating the period of the vibratory motor,whereby it may be maintained in synchronism with the time deement.

17 In a time keeping apparatus, the combination of a vibratory motor,an-escapeinent wheel driven by said motor, a rocker arm driven by saidescapement havmg a periodic oscilwheel, a time determining element'latory motion, a drivin spring stressed by said time determinin eement, said driving spring being arrange to receive mechanica energyfrom the operation of the rocker arm vibration of the time determiningelement, and an electric contact periodically operated b said timedetermining element for contro ing the application of power to thevibratory motor. a

18. In a time keep apparatus, the combination of a time determiningelement having eriodic motion of oscillation, a spring driving elementstressed by said element and urgingsaid element in one direction, avibratory motor of the electro-magnetic type having an electric circuit,said spring element serving also as conductor in said circuit, anelectric contact operated by the movement of said spring forperiodically closing the circuit of said vibratory motor, means operatedby the vibratory motor for opening the circuit, the power inputincreasing with increasing lag of the motor, whereby the vibratory motorand the time determining element are maintained in synchronism.

19. In a time keeping apparatus, the combination of a vibratory motor ofthe electro magnetic type, a tooth rotated by said motor in alternatedirection, a fork engaged by said tooth in a portion of its swing, thetooth swinging free of the fork at the exremes of its swing, palletsoscillated by said fork, an escapement wheel having teeth driven by saidpaliets, a pinion rotated by the escapement wheel, a gear train drivenby said pinion, a rocker arm operated by engagement with the teeth ofthe escapement wheel, a time determining eiement having a periodicmotion of oscillation, a spring driving element stressed by saidelement, the rocker arm being arranged to transmit methanical energy tosaid spring at each oscillation of the time determining element, thespring also being in the electric circuit of the motor, an electriccontact in said circuit arranged to com plate the circuit when thespring swings into contact with it, the circuit being broken when thedriving spring receives its mechanical ener whereby the vibratory motorand the time determining element are maintained in synchronism,

20. in a-time keeping apparatus, the com-- bination of a vibratory motorof the electromagnetic type, a tooth rotated by said motor in aitcrnatedirection, a fork engaged by said tooth in a portion of its swing, thetooth swinging free of the fork at the extremes of its swing, palletsoscillated by said fork, an escapement wheel havin teeth driven by saidpallets, a pinion rotat by the escapement wheel, a gear train driven bysaid pinion, a rocker arm operated by en agement with the teeth of theesca ement wheel, a time determining element aving a periodic motion ofoscillation, a spring driving element stressed by said element, therocker arm being arra d to transmit mechanical energy to said 1 springat each oscillation of the time determining element, the spring alsobeing in the electric circuit of the motor, an electric contact in saidcircuit arranged to complete the circuit when the spring swings intocontact with it, the circuit being broken when the driving springreceives its mechanical energy,

and an adjustable screw carr'ed with the time determimng element, saidscrew engagmg said spring periodically to withdraw it out of contactwith the rocker arm, whereby the vibratory motor and the timedetermining element are maintained in synchronism.

21. In a time keeping apparatus, the comtam it in operation, and meanscontrolled b bination of'a time determining element having a periodicmotion, a vibratory motor element, and an electro-magnetic means formaintaining the motor element in vibration, said electro-magnetic meansbeing jointly controlled by the time determining element and thevibratory motor element, whereby the vibratory motor element and thetime determining element may be maintained in synchronism.

22. In an electric clock, an electrically actuated vibratory motorhaving a control circuit effective at each beat of the motor, and meansfor varying the amount of energy delivered to the motor at each beatautomatically whenever its vibratory rate deviates from a desired normalrate whereby the. period of the motor may be regulated and maintainednormal.

23. In an electric clock, an oscillatory time keeping element, avibratory motor, means including an electric circuit for deliveringimpulses to said motor at each beat to ma insaid element for varying theenergy delivered to said motor at each beat in a manner to vary theperiod of said motor and synchronize the oscillations of the motor withthose of said element.

24. In an electric clock, the method of synchronizing the oscillationsof an electricall which comprises givi said motor a natural period ofoscillation s ightcontrolled'by said driven by said pal determiningtuated vib 1y different from that of said varying the energy deliveredto the motor at each beat proportionally to the extent that theoscillations of the motor and element are out of step with one another,so as to temporarily change the period of said motor, and maintain it inoscillation synchronously with said element.

25. In a time keeping apparatus, the combination of a vibratory motorhavin a va riable amplitude of vibration, osci atory gearing arranged tobe driven during the middle portion free at the extremities of itsvibration, pa ets periodically oscillated by said gearin an escapementwheel ets, an oscillating time element, and means coacting tween saidelement and said esca ement, wheel for controlling said motor an keepingit automatically in synchronism with said element and keeping saidelement in oscillation.

26. -In an electric clock, an electrically acratory motor havin acontrol circuit efiective at each beat 0 the motor, an oscillatory timeelement, means element for varying the amount of energy delivered to themotor at each beat in accordance with the degree of saidelement andmotor,

synchronization of element, and

of the vibration, the vibrab tory-motor swingin whereby the period ofsaid motor may be maintained in synchronism with said element, and meanscontrolled by said motor for delivering an impulse to said element atintervals to maintain it in oscillation.

27. In an electric clock, an oscillating time measuring element meansengaged and stressed by said element While said element is moving in onedirection from an intermediate position, and imparting'an impulse tosaid element during its return movement towards said position, and meansoperable upon said first means while said element is continuin theremainder of a complete 0scillation ibr varying the point at which saidfirst means is engaged by said element, whereby the propelling action ofsaid first means will be reater than its retarding action and said eement will be maintained in oscillation.

28. In an electric clock, an oscillating time measuring element, aspring device engaged by said element to retard yieldingly its moveyment while approaching one end of its arc of y ment of the action ofsaid spring device duractuated vibratory motor with those of a tlmekeeping element,

mg the remaining portion of a complete oscillation of said element, andmeans operable on said spring device to move it in the direction inwhich it is moved while retarding the oscillation of said element,whereby the retarding action of said spring device on said element willbe less than the propelling action on said element, and said elementwill be maintained in oscillation.

29. In an electric clock, an time measuring element, a spring deviceengaged by said element to retard yieldingly its movement whileapproaching one end of its arc ofoscillation, and urging said element inthe o posite direction during the ginning of the return swing of saidelement from said end, means engaged by said spring device at anintermediate position in t e oscillation of said element for relievingsaid element of Vice during the plete oscillation operable on saidspringdevice to move it in t c direction in which it is moved whileretarding the oscillation of said element, whereby the retarding actionof said spring device on said element will be less than the propellingaction on said element, and said element will be maintained inoscillation,

oscillating the action of said spring deremaining portion of a comsaidfirst means being adjustable to vary of said element, and means tion ofsaid pendulum, a stop engaged by erable the free end of said spring,with said spring flexed in one direction of oscillation of saidpendulum, whereby said spring will be urged resiliently against saidstop, said pendulum having means engageable with the free end of saidspring to flex it away from said stop while said pendulum is swinging inone direction away from an intermediate position, whereby sa1d springwill retard such movement of the pendulum, and will propel said pendulumin a reverse direction after said pendulum reaches the limit of itsflexing operation and starts a return swing, the pendulum releasing saidspring and continuingits oscillation after the spring engages said stopuntil the pendulum completes a cycle of oscillation, and means opduringthe movement of said pendulum while free from the action of said springsaid stop to make the retarding action of said spring less than thepropelling action, whereby the pendulum will be maintained inoscillation.

31. In an electric clock, an oscillating time measuring element,propelling means engaged and stressedby said element during movement oisaid element in one direction away from an. intermediate position, andpropelling said element in the reverse direction during the returnmovement to said intermediate position, said element being 'free tocomplete its cycle of oscillation uninfluenced by said propelling means,and

means rendered effective automatically by said propelling means whensaid element passes said propelling movement for stressing saidpropelling means in the direction in which it is stressed by saidelement.

32. In an electr1c clock, an oscillating time measuring element, aspring device engaged by said element and stressed during movement ofsaid element in one direction from an intermediate position in itsoscillation,

and propellingsaid element during the return movement to saidintermediate position, a stop engageable 'by said spring at saidintermediate position for relieving said element from'the action of saidspring during completion of a cycle of oscillation of said element,means including an electric circuit closed by the engagement of saidspring'device with said stop for stressing said spring device in thedirection of its movement away from said intermediate position, wherebythe retarding .action of-said-spring will be of shorter duration thanthe ropelling action, and said element will lie maintained inoscillation.

33. In an electric clock, an oscillating time measuring element, aspring device enfor flexing said spring away from,

gaged by said element andstressed during movement of said element in onedirection from an intermediate position in its oscilla tion, andpropelling said element during the return movement to said intermediateposition, a stop engageable by said spring at said intermediate positionfor relieving said element from the action of said spring during'completion of a cycle of oscillation of said element, an electriccircuit closed by engagement of said spring device with said stop atapproximately said intermediate position of said element, anelectrically actuated vibratory motor maintained in synchronism withsaid element by said circuit, and means controlled by said motor whilesaid element is completing its cycle of oscillation free of the actionof said spring device for stressing said spring device in the directionin which it is stressed by said element at the beginning of said cycleof oscillation from said intermediate position, whereby the retardingaction of said spring device on said element will be less than itspropelling action thereon, and said element will be maintained inoscillation.

34;. Ina horological device, an accurate time keeping unit, a poweractuated time keeping unit, means-controlled jointly by said units forregulating the rate of operation of said power operated unit in a mannerto cause it to operate in approximate synchronism with said first unit,and means operated by said power actuated unit for supplying drivingenergy to said first unit. In witness whereof I have hereunto set myhand this 22d day of March, 1927'.

, ARTHUR F. POOLE.

intermediate position during said k

